Diaphragm Pressure Pod for Medical Fluids

ABSTRACT

A tubular medical fluid flow set comprises a pressure sensing chamber connected in flow-through relation to fluid flow tubing of the set. The pressure sensing chamber defines a movable, flexible, impermeable diaphragm dividing the chamber into two separate compartments. The fluid flow tubing communicates with one of the compartments and is isolated from the other of the compartments. A port is carried on the chamber, the port having a seal therein, and communicating with the other of the compartments. Thus, the other of the compartments is hermetically sealed until the port is opened for connection with a pressure measuring device, to keep the flexible diaphragm in a desired, initial position prior to opening of the seal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/195,558 filed Jun. 28, 2016, which is a continuation of U.S.application Ser. No. 13/928,454, filed Jun. 27, 2013, now U.S. Pat. No.9,393,397, which is a divisional of U.S. application Ser. No.13/299,868, filed Nov. 18, 2011, now U.S. Pat. No. 8,491,518, which is adivision of U.S. application Ser. No. 11/270,080, filed Nov. 9, 2005,now U.S. Pat. No. 8,092,414, all of which are hereby incorporated byreference herein in their entireties.

BACKGROUND

Sets for extracorporeal blood handling, and also parenteral solutionsets, generally require flow-through chambers, often called dripchambers, which, in use, utilize an upper liquid level of the medicalliquid passing through it, with an air space on top. Such chambersgenerally have a permanently connected, branching, hollow-bore,flexible, branch line communicating with said air space for an airpressure line which connects via a reversible connector at its remoteend to an equipment pressure port on the permanent equipment, which inturn communicates with a pressure monitor transducer for measuringair-pressure in the chamber as a surrogate for blood-pressure. Apressure-transmitting sterility barrier or diaphragm separates thesterile, disposable set and the unsterile permanent equipment.

These sets generally need to be initially primed with saline or anotherparenteral solution, where the proper upper liquid level is provided ineach drip chamber present. Then, in the field of extracorporeal bloodhandling such as in hemodialysis, connection may be made with a fistulaset or other means of access to the patient's bloodstream, and thesaline in the primed set is replaced by blood, which is transferred toand from an extracorporeal blood processing device. These devices maycomprise hemodialyzers, hemofilters and other devices for extractingcomponents in the blood and returning the balance to the donor.

Alternately, it is also known for a flow-through chamber to incorporatea diaphragm as the pressure-transmitting sterile barrier which may be indirect contact with blood or another parenteral solution, or may only bein contact with air above the upper liquid level. For example, seeMadsen et al. U.S. Pat. No. 3,713,341, Borsanyi U.S. Pat. No. 3,863,504,and Gangemi U.S. Pat. No. 4,077,882.

As taught in Brugger et al. U.S. Pat. No. 5,693,008, a flow-throughchamber or “pod” is provided, having a diaphragm that transmits pressurebut prevents passage of blood across said diaphragm. The pod comprises arigid chamber in which said diaphragm is mounted and which furthercomprises a reversible connector which communicates with an airspacebetween said connector and the non-sterile side of said diaphragm. Saidreversible connector, air space and non-sterile diaphragm side are opento atmosphere prior to medical treatment. To prepare for treatment, thereversible connector is connected directly to the pressure port on theface of the dialysis machine. Thus, a pressure tight system is attainedand the machine's pressure transducer can measure pressure in thesterile set's flow-through blood pathway. Flow-through blood tubing mustconvey blood to and from that pod mounted on the face of the machine.

As a disadvantage of these diaphragmatic systems, the great majority ofover 100,000+ dialysis machines which are clinically used at the presenttime have their pre-pump arterial, post pump arterial and/or venouspressure ports for measuring blood pressure positioned on the face ofthe machine remote from other sites to which the blood tubing must berouted, such as the to the blood pump, the dialyzer (in the case ofhemodialysis), the safety shut-off clamp, etc. Thus there is adisadvantage in the use of this system. It is always desirable tominimize the length of the extracorporeal blood flow path, both forreasons of simple economy, to minimize extracorporeal pressure drop andclottable surface area, as well as to minimize the total extracorporealblood volume.

It is a further disadvantage of the current diaphragmatic system thatthe non-sterile side of the diaphragm is open to atmosphere prior tobeing brought into sealing relation with the equipment's pressure port,and therefore may be displaced prior to use. Such displacement resultsin pressure measurement errors and/or limited pressure measurements.

It is a disadvantage of sets which fit the great majority of the world'sdialysis machines that they have drip chambers and permanently attachedbranch lines. Such branch lines complicate the sets' construction,packaging and use and are expensive.

By this invention, a generally airless pressure chamber (called a “pod”)which contains a diaphragm may be used as a substitute for a pressuremonitoring drip chamber regardless of the front panel placement ofnecessary equipment. By this invention the pod is not connected to thepressure port on the face of a dialysis machine, but is spacedtherefrom, and the important function of pressure monitoring still takesplace. This achieves numerous advantages when compared with the priordrip chamber. Specifically, in the pod of this invention, it becomesunnecessary to set a liquid level as in many prior art chambers, and ablood-air interface can be completely avoided. At the same time, thechamber of this invention may be significantly smaller than the dripchambers of the prior art, and thus may have a reduced priming volume.Also, the volume of the chamber can be temporarily further reduced bymanipulation of the diaphragm, for example during the rinse back step inextracorporeal blood handling procedures such as dialysis, to reduce theamount of solution needed in the rinse back process.

Also by this invention there are achieved important advantages whencompared with the pods of the prior art. Compared with the primingvolume and tubing costs of extracorporeal circuits using pods of theprior art, this invention saves cost because less large-bore bloodtubing, but more small bore air pressure monitoring tubing, is used, thelatter not containing blood. Thus it can be of a much finer, andcheaper, gauge than blood tubing, resulting in a net savings of plasticand cost, with less blood volume.

Sets utilizing the pod of this invention are easier to prime andoperate, because there is no liquid level needed to be set in a chamber,as in the prior art. The pod of this invention may have branchconnections for access to parenteral solutions such as saline or heparinsolution, and it also may carry a connected, blood-free pressure monitorline (pressure tubing) for connection to a remote pressure port, for themonitoring of particularly blood pressure in the tubular set whichcarries the chamber. Cost may be saved in the manufacture and assemblyof the set of this invention, since the blood tubing may be shortened,as it does not have to extend to the face of the dialysis machine, whilealso reducing extracorporeal blood volume (priming volume), as aclinical advantage.

The pod of this invention may be positioned precisely where pressureneeds to be determined. For example, to detect line kinks or leaks, thepressure measuring chamber or pod should be upstream of the tubing whichmay leak or become kinked. Where a dialyzer is remotely monitored from amachine (as is generally the case) the placing of a pressure measuringchamber or pod immediately downstream from it is impossible in the caseof drip chambers or prior art pods. As a further advantage, the pressurechamber of this invention does not require a permanently connectedpressure monitor line. Rather, it can connect with a reusable pressuremonitor line. Thus the set utilizing the chamber is less expensive, andthere is an overall saving of cash because many disposable sets may besequentially used with a single pressure monitor line, if desired.

SUMMARY

In accordance with this invention, a tubular blood flow set is providedwhich comprises a pressure sensing pod connected in flow-throughrelation to fluid flow tubing of said set, typically blood tubing. Thepressure sensing pod defines a movable, flexible, impermeable diaphragmdividing the pod into two separate compartments. The fluid flow tubingcommunicates with one of the compartments for fluid flow through thecompartment. The fluid flow tubing is isolated from the other of thecompartments by the diaphragm. A pod connector carried on the podcommunicates with the other of the compartments. In one embodiment ofthis invention a hollow-bore branch line is permanently attached to andcommunicates with the pod connector. The branch line is long enough, andterminates in a releasable connector such that it mates with themachine's pressure port. In another embodiment, the pod connector isreleasable, and may be temporarily attached to a separate branch linebearing an appropriate mating connector for the pod connector. Asbefore, the branch line is long enough, and terminates in a releasableor non-releasable connector to the pressure sensing machines pressureport. Preferably, the pod connector is sealed prior to attachment toeither the machine port directly, or preferably to said separate branchline. Such sealing may be permanently breached, as in a frangiblebarrier, or it may be reversibly opened such as attained by a slit discof U.S. Patent Publication No. US 2005/0159710 A1, the disclosures ofwhich are incorporated by reference.

Thus, the one compartment of the pod is part of a fluid flow path,typically blood, through the fluid flow set and the pressure sensingchamber. The other of the compartments is preferably hermetically sealedby a sealed port, until opened for connection with a pressure measuringdevice. The effect of this is to keep the movable, flexible diaphragm ina desired, initial position prior to said opening. The diaphragm, whenthe hermetic seal is broken, is capable of moving between a firstposition and a second, opposed position in which the diaphragm in thefirst position can bow outwardly from the blood pathway, to maximizeblood volume in the chamber, while the diaphragm in the second positioncan bow inwardly to minimize, but typically not eliminate, blood volumein the chamber. In some embodiments, the diaphragm has a central, domedportion which can flip between the two positions.

In an arterial, pre-pump pod embodiment where the pod is generallysubjected to negative pressure [but sometimes positive pressure whenpriming], the diaphragm may be moveable between the first and secondpositions when the hermetic seal is broken, but not before. The sameholds for the post pump, positive pressure situation.

In some embodiments, the sealed port is opened by engagement with aconnector which is carried on an end of a length of separate pressuretubing. This connector may be, for example, a male luer lock connectoror any other desired connector that is compatible for connection withthe sealed port carried on the pod. Also, the pressure tubing connectsat an opposed end thereof with the pressure measuring device, eitherpermanently or separably, as may be desired.

Specifically, in some embodiments the sealed port of the pod may be sosealed by a partition having a peripheral connection with a lumen wallof the sealed port. A major portion of the peripheral connection isrelatively thin, capable of being easily broken open, while a minorportion of the peripheral connection is thicker than the major portionof the peripheral connection, so that the minor portion functions as ahinge. Thus the partition can pivot, but it cannot separate from therest of the sealed port as it is torn open by an advancing connectorsuch as a male luer.

In some embodiments, the sealed port partition is relatively thin in aline of tearing weakness extending across the partition, as well asaround most of the periphery so that, when broken, there are two hingesand half partitions which distend a lesser distance inwardly than theprevious embodiment.

Further, by this invention in some embodiments, a first section of thepartition adjacent to the major portion (but radially inwardlytherefrom) is thicker than the corresponding, opposite section of thepartition adjacent to the periphery thereof. The effect of this is tofocus rupturing force provided by pressure from a male luer or othertubular connector to the periphery of the partition at the firstsection. Thus, when a normal, flat-ended tubular connector is insertedinto the sealed port and pressed inwardly, it encounters the firstsection and presses against it, without contact with the oppositesection. Accordingly, the rupturing force is focused against only aportion of the periphery of the partition, that portion being at leastpart of the major portion of the peripheral connection, thin enough tobe easily broken open. This force is focused because the tubularconnector is engaging only the first section of the partition because ofits increased thickness, and not the corresponding, opposite section.Thus the total force required for frangibility of the partition is less.The partition easily opens and pivots about the minor portion of theperipheral connection, to open the sealed port.

Typically the first section of the partition is at least twice as thickas the corresponding, opposite section.

Thus, a blunt tube such as a male luer can easily open the partition.

Further in accordance with this invention, a pressure sensing chamber orpod for a tubular medical flow set described above may be directly andpermanently attached to an inlet or outlet connector, for direct,typically releasable, connection with an extracorporeal blood processingdevice. The set that carries the chamber is for handling extracorporealblood flow, with the pressure sensing chamber being directly attached,preferably to the downstream end of, the extracorporeal blood processingdevice such as a hemodialyser. The pressure monitor system that utilizesthe pressure sensing pod is thus capable of monitoring pressure of theentire length of the blood flow tubing extending downstream from theextracorporeal blood processing device, typically a dialyzer. This is asignificant area for pressure monitoring, because it is typically themajority of the extracorporeal blood flow circuit that operates underpositive pressure. A serious blood leak or kink anywhere along the linedownstream of the dialyser can thus be detected by a pressurefluctuation, if there is constant monitoring through the pressuresensing chamber.

Generally, the diaphragm of the pod occupies substantially a firstposition when the interior of the flow set is filled with a blood atclose to atmospheric pressure, as when the pump is stopped or duringpriming, and the diaphragm is urged towards the second position wheneverthe blood side pressure on the diaphragm is less than the air sidepressure on the diaphragm. Such greater air side pressure may beintentionally applied through said pressure tubing, which may beflexible, by a machine system having an air pump communicating with saidtubing, or the pressure tubing may be disconnected from the machine'sport and reconnected to a device such as a syringe. In either case,positive pressure may intentionally be applied to the chamber to drivethe diaphragm towards the second position, which may be desirable duringa blood rinseback procedure, involving rinsing blood from the tubularset, back to the patient, since the internal volume of the chamber isminimized by such intentional pressurization, thus reducing thehydration that must be provided to the patient. The tubing may carry aclamp or valve to retain the positive pressure at the diaphragm.

Alternately, the pod of this invention may comprise an arterialpost-pump and/or venous pod embodiment where the pod is generallysubjected to positive pressure. The diaphragm may substantiallyinitially occupy the second position when the interior of the flow setis filled with blood at close to atmospheric pressure; and the diaphragmis urged towards the first position whenever the blood side pressure isgreater than the air side pressure on the diaphragm, so that the greaterthe blood pressure, the more the diaphragm is driven from the secondposition toward the first position.

Movement of the diaphragm between the first and second positions isrestricted by the fact that, in the pressure sensing process, a sealed,fixed volume of air exists between the diaphragm and a pressure sensingtransducer, with the branch line pressure tubing extending therebetween.Thus, movement of the diaphragm toward one position or another positionwill reflect a change of the level of compression of the air or othercompressible fluid in the fluid flow path between the diaphragm and thepressure sensing transducer, thus transmitting the pressure of the bloodto the transducer. Thus, in this circumstance, the diaphragm does notflip back and forth with ease between the first and second positionsbecause of the sealed volume of air or other compressible fluid in theflow path between the diaphragm and the pressure transducer.

Further in accordance with a preferred embodiment of this invention, thesealed port communicating with the other of the compartments of thepressure sensing chamber facilitates the priming of the medical fluidflow set, since it provides the sealed, fixed volume of air discussedabove that holds the diaphragm in the desired position. This desiredposition may vary, depending on whether the pod is to be exposed toreduced pressure or elevated pressure during normal operation.

One can see that if the other of the compartments separated from fluidflow by the diaphragm is not sealed, the diaphragm will flip from oneposition to the other in accordance with pressures that are encounteredin the fluid (blood) flow path during shipping, installation or priming.If the diaphragm winds up in the wrong position at the end of priming,inconvenient steps will have to be taken, while maintaining sterility,to remedy it.

Thus, the sealed port holds the diaphragm in its desired position, whichposition depends upon its contemplated use, until priming or otherdesired step(s) has been completed. Then, one can open the seal of thepressure sensing pod port as a sealed connection is made with a pressureline, so that now the pod is again sealed with the pressure linecommunicating between the chamber and the pressure monitor.

Specifically, when the blood flow set of this invention is being used asan arterial set for hemodialysis, upstream from the roller pump tubingso as to encounter negatively pressurized blood (i.e., blood undersuction pressure from the roller pump), it may be preferred for the poddiaphragm at ambient pressure to initially occupy a positionsubstantially close to the first, volume maximizing position. Thus, asnegative (subatmospheric) bloodline pressure increases, the diaphragmmoves incrementally toward the second position, with that movement beingresisted by the sealed, fixed volume of air, which is being expanded inresponse to the negative (subatmospheric) pressure of the blood actingupon the diaphragm. Thus, the negative pressure is duplicated in thefixed volume of air or other compressible fluid, and may be sensed bythe pressure transducer, which is positioned remotely from the pressuresensing chamber and diaphragm used in this invention. Under positivepressure blood line conditions, the diaphragm starts generally at theopposite, first position. However, when there is open or ambientpressure on both sides of the diaphragm, the diaphragm may flip back andforth between its first and second positions relatively easily.

The above-described chamber or pod may have a bottom wall, which furtherdefines a channel having a wall of U or V-shaped cross section.Accordingly, when the diaphragm is forced into its extreme, secondposition, fluid flow is not blocked through the channel, so that flow isprovided in all circumstances through the medical fluid flow set.Specifically, the channel wall may be U-shaped and substantiallycontiguous with the internal diameter wall of the flow tubing of theset, preferably being substantially aligned with, and of a size similarto, the inner diameter wall of the flow tubing of the set where itconnects with the chamber. This can promote efficient fluid flow throughthe entire set, even when the diaphragm is held in its second, bloodvolume minimizing position.

Also, one or more access ports may be provided to the pod's inlet oroutlet connection or the pressure chamber communicating with its bloodpathway. These ports may be used to provide parenteral solution,heparin, or other medicaments to the blood or for withdrawing blood orair or saline from the flowpath.

The pod may be connected at one end via a flowthrough port with the pumptubing of the set, which comprises typically roller pump tubing, whichis carried on many extracorporeal blood transport sets. Alternately, theflowthrough port may connect with another pump apparatus, or it mayconnect to a venous air-trapping chamber, or any other flowthroughcomponent of an extracorporeal set. The pressure chamber (pod) then hasanother end with another flowthrough port which may fit tubing of sameor different diameter from pump tubing or to another flowthroughcomponent. Thus, this pod may serve the additional function of a pumpsegment connector, a tube connector, or a device connector, as well asproviding other function as described herein.

Further by this invention, blood may be rinsed from the extracorporealblood flow tubing and returned to the patient, after an extracorporealblood flow procedure such as hemodialysis. The blood flow tubing isconnected to the pod having the flexible diaphragm, which defines ablood holding volume. The diaphragm is sealingly mounted within thechamber. This method comprises the steps of pressurizing the chamber tomove the diaphragm, to cause the blood holding volume of the chamber tobe substantially minimized, without blocking blood flow through theblood flow tubing and chamber. Then, parenteral solution such as salineis caused to pass into the tube and chamber to replace the blood, whilethe blood is returned to the patient. The substantially minimized bloodholding volume of the chamber reduces the fluid volume of theextracorporeal blood flow tube, which provides clinical advantage, andrequires the use of less solution to provide the desired rinseback.

Typically, this method is practiced after the step of using the pod tosense blood pressure in the blood flow tube during extracorporeal bloodprocessing, with the diaphragm being positioned to enlarge theblood-holding volume in the chamber above the minimum volume, a lengthof pressure tubing extending from the chamber to a pressure monitordevice

Further by this invention, a pressure transmitting pod defines achamber, the pod being for connection and flow-through relation to fluidflow tubing of the fluid flow set. The pod has a flexible fluidimpermeable diaphragm dividing the pod into separate compartments. Thefirst of the compartments communicates with flow connectors for thefluid flow tubing. A second of the compartments communicates with apressure connection port for connection with the length of pressuretubing at one end thereof. The tubing is for sealed connection at itsother end to a remote pressure connector of a pressure sensing machine,to transmit pressure from the second of the compartments through thepressure tubing to the pressure sensing machine for pressure monitoring.The diaphragm has a dome shape, and is sufficiently flexible to easilydistort in a manner reflective of pressure changes, to vary the volumesof the two compartments. In some embodiments, the diaphragm of domeshape can vary the volume of the respective compartments at a pressurevariation of 500 mm. mercury by at least 3 cc.

The pressure tubing may be permanently connected to the connection port,the pod, or releasably connected as previously described. The pressuretubing at its other end can connect to a remote tubing connector forconnection to the machine remote pressure port during medicaltreatments, or permanently, if desired. As previously described, the podconnection port is sealed from the atmosphere by an internal partition,the seal being openable by sealing attachment with a connector of thepressure tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is a partially diagrammatic, sectional view of aportion of a first embodiment of a tubular blood flow set using thepressure sensing pod and flexible diaphragm disclosed.

FIG. 2 is an exploded, perspective view of the pressure sensing pod ofFIG. 1

FIG. 3 is a plan view of the pressure sensing pod of FIG. 1.

FIG. 4 is a longitudinal sectional view taken along line 4-4 of FIG. 3.

FIG. 5 is a transverse, sectional view taken along line 5-5 of FIG. 3.

FIG. 6 is an end elevational view of the chamber of FIG. 3.

FIG. 7 is a plan view of a hemodialysis set, making use of anotherembodiment of this invention.

FIG. 8 is an exploded, longitudinal sectional view of a pressure sensingpod of the set of FIG. 7.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is a fragmentary, enlarged plan view of a portion of FIG. 7,showing the connection of the pressure sensing pod of FIG. 8.

FIG. 11 is a detailed view of FIG. 8, showing how a connector such as amale luer lock connector can rupture the partition for access to thepressure sensing pod.

FIG. 12 is a view similar to FIG. 9 of another embodiment of the sealedport partition

FIG. 13 is a sectional view taken along line 13-13 of FIG. 12.

FIG. 14 is a fragmentary view of the sealed port of FIG. 13, carried ona pod as in previous embodiments, about to be connected with a pressuretube as in previous embodiments.

FIG. 15 is a sectional view showing an initial connection (of luer locktype) of the components of FIG. 14.

FIG. 16 shows a fully advanced, sealed connection of the components ofFIG. 14, with the partition of FIG. 12 being opened by advancement ofthe male luer lock connector.

FIG. 17 is a perspective view of the connector of FIG. 14, showinginternal parts.

FIG. 18 is a plan view of another embodiment of the pod of thisinvention.

FIG. 19 is a sectional view taken along line 18-18 of Fig. A.

DETAILED DESCRIPTION

Referring to the drawings, FIG. 1 shows a portion of a venous set 10 forhemodialysis, conventional except as otherwise shown. Set 10 is shown tocomprise a length of roller pump tubing 11, which is conventionallyattached to one end of pressure sensing pod chamber 12 of thisinvention. The opposed end 14 of pod 12 may connect to a length of settubing 16, which may connect to other set components, which may be ofconventional design for an extracorporeal blood conveying set.Particularly, tubing 16 may fit within the inner diameter of end portion14 so that such tubing is of a different inner diameter from that ofpump tubing 11, if desired. Thus, pressure pod 12 also includes thefunction of a connector for joining together tubing of differingdiameters in the blood set.

Similarly, the end 18 of pump tubing 11 may connect through aconventional connector, such as one shown in U.S. Pat. No. 5,360,395,(the disclosures of which are incorporated by reference) to a length oftubing 20 to connect additional, conventional portions of a tubularblood set for hemodialysis or another extracorporeal blood treatmentprocedure. For both tubes 20 and 16 these may include injection sites, Ysites, and end connectors, which may connect in this present embodimentrespectively with a dialyzer and the patient, but in other embodimentscould connect with a different, extracorporeal blood processing device,or any other conventional connection.

FIG. 2 shows an exploded view of pressure pod 12, comprising a lowercompartment-defining portion 22, an upper compartment-defining portion24, and a flexible diaphragm 26, which defines a convex, central portion28 shown to be bulging outwardly from the blood flow portion of thechamber. Compartment defining portion 22 defines a blood inlet port 30and a blood outlet port 32, as well as an access port 34, whichcommunicates with the interior of the chamber. Each of these ports 30,32, 34 may be connected to flexible tubing in a conventional manner. Asshown in FIG. 1, ports 30, 32 connect with blood flow tubing, while port34 can connect with tubing 35 which, in turn, may connect with a sourceof parenteral solution such as saline, or a source of heparin solution,or any other desired or conventional use. Tubing 35 connects with theinterior of pressure pod 12 through aperture 38.

The three components 22, 24, 26 of pressure pod 12 seal together withperipheral, circumferential connection, and may be conventionally bondedtogether by conventional means such as ultrasound sealing or solventbonding, the components being made typically of conventionalthermoplastic and/or thermoset materials, to form the completed chamberas shown in FIGS. 3 to 6. Upper compartment-defining portion 24 as shownin FIG. 2 may be rotated by 180 degrees to form the assembled deviceshown in FIGS. 1, 3 and 4.

Thus, flexible diaphragm 26 is shown in the assembled pod 12 as beingsealingly mounted within a pressure sensing pod between connections ofthe blood flow tubing 30, 32 and a connection port 40, which may have aseal such as a known valve, or a frangible barrier. Port 40 may connectwith a length of pressure tubing 42 (FIG. 1), which is thus connectedwith the interior of upper compartment-defining portion 24 of pressuresensing pod 12. In FIG. 1, diaphragm 26 is shown to be occupying itsfirst position as previously described, where diaphragm 26 initiallybows outwardly to maximize the chamber volume communicating with theblood flow tubing 11, 16. When the blood flow within pod 12 is undernegative or subatmospheric pressure, as is the case for portions of set10 which are upstream of roller pump tubing 11, a suction is induced ondiaphragm 26, causing it to be urged downwardly toward inlet and outletports 30, 32 in position 26 a. Pressure tubing 42 is long enough so thatit will reach pressure measuring equipment connector 41 mounted anywhereon the equipment. Equipment pressure connector 41 communicates with apressure transducer 43 as in a conventional hemodialysis machine, forexample, communicating by the joined end connector 44 of tube 42 andconnector 41 with the air space within tube 42 and above diaphragm 26.This air space can be sealed when connectors 44 and 41 are joined, sothat air neither is added to nor escapes from the volume of air present.

Thus, as suction from the negatively pressurized blood below diaphragm26 is exerted, an expansion of the fixed volume of air described abovetakes place, which will allow diaphragm 26 to move downwardly until thenegative (subatmospheric) pressures on both sides of the diaphragm arebalanced. Thus, the air pressure in tube 42 will match the pressure ofthe blood below diaphragm 26, and that air pressure can be sensed bypressure sensor 43, and reported by an appropriate signal on preferablya moment-by-moment, real time basis, as is important in the field ofextracorporeal blood handling.

FIG. 4 shows how diaphragm 26 can be moved to its second position 26 a,in which it bows inwardly with respect to the blood flow path, tosignificantly reduce the blood volume in chamber 10. Diaphragm 26 may beinitially held in this position for the measurement of positive,super-atmospheric pressures in the blood flow path 46, where increasesin pressure urge diaphragm 28 outwardly from near the second position 26a (FIG. 4) toward the first position 26 (FIG. 1). However, as before,this movement is resisted by the fact that there is a constant amount ofair the space 48 above diaphragm 26 and in pressure tube 42. The airpressure in pressure tube 42 equals the blood pressure in flow pathportion 46, with diaphragm 26 moving to make it so, so that the bloodpressure can be monitored by transducer 43 while the unsterile pressureconnectors 41, 44 remain remote from any blood, being conventionallycarried on the face of a dialysis machine or the like at a positionspaced from the arrangement of the roller pump, pump tubing 11, andchamber 12. Because of the presence of pressure tubing 42, which extendsto connector 41 and pressure transducer 43, wherever it may be locatedon or in the dialysis machine, it is possible to shorten the overalllength of the blood tubing 16, 11, 20, which is desirable for reasonsstated above.

The lower compartment portion 22 of pod 12 has a bottom wall whichdefines a transverse channel 50, which extends between blood inlet port30 and blood outlet blood port 32. Channel 50 is shown to be of U-shapedcross-section, being substantially aligned with, and having a sizesimilar to, the inner diameter of the blood flow port 30, 32 and thetubing which they carry, to provide efficient fluid flow, even whendiaphragm 26 is in its second position, as shown in FIG. 4 as diaphragm26 a. The presence of channel 50 assures that there will not be majorblocking of blood flow when diaphragm 26 is in its second position.

When the extracorporeal blood processing procedure is complete, it isnecessary to rinse the blood back to the patient in a step known as“rinse back.” To accomplish this, pressure tubing 42 may be disconnectedfrom the pressure monitor transducer 43, and the portion of the setwhich draws blood from the patient can be removed from the patient.Then, pressure tubing 42 is connected with a conventional syringe 52(FIG. 1), which is depressed to add air or other fluid to the system tocause diaphragm 26 to assume its second position as shown in FIG. 4 (26a). A slide clamp 54 or other type of clamp then may close off pressuretubing 42, to keep diaphragm 26 under pressure and firmly in its secondposition 26 a during the rinse back process, so that the bloodcontaining volume of pod 12 is minimized. Saline solution or the likeflows into the system through an access site such as parenteral solutionline 35, to replace blood in the set with saline solution, and to returnblood back to the patient through the remaining patient connection.Alternatively or additionally, saline solution may be added to theseparated end of the set of set portion 16 for rinseback, to terminatethe procedure.

Thus, by one embodiment of this invention, blood pressure in a bloodflow tube may be monitored through a length of pressure tubing 42connecting to a diaphragm pod 12 as described, with the diaphragm beingpositioned near a first position that essentially maximizes the bloodholding volume in the pod, although varying, for example negative,pressures in the chamber can result in differing positions of thediaphragm. Then, at the end of the extracorporeal blood flow procedure,pressure sensing pod 12 may be pressurized to move diaphragm 26 to itssecond position 26 a, to cause the blood holding volume of the pod to besubstantially minimized, without blocking flow through the blood flowtube and pod. Parenteral solution such as saline is then passed into thetube and pod to replace the blood, while the blood is returned to thepatient.

Referring to FIGS. 7-11, another embodiment of the invention is shownfor an extracorporeal system for hemodialysis.

Arterial set 60, for removing blood from the patient, comprises aconnector 62 for connection with a patient fistula. A length of flexibletubing 64 communicates with an injection site 66 which, in turn, isdirectly connected to a pressure sensing pod 68, similar to that shownin FIG. 8. Pressure sensing pod 68 connects with pump tubing 70, havinga larger diameter than tubing 64. Tubing 70, in turn connects with aconnector 72 for connection with lesser diameter blood flow tubing 74,which, in turn, connects with dialyzer 76. The dialysis solution flowlines are eliminated for clarity of disclosure. Solution line 69connects with pod 68 in a manner similar to line 35 of FIG. 2.

Dialyzer 76, in turn, connects directly to a connector 78, ofconventional design, which, in turn, connects directly to anotherpressure sensing pod 80 of a type disclosed in FIG. 8 and otherdrawings. Thus, pressure sensing pod 80 can be disconnected fromdialyzer 76 to permit reuse of dialyzer 76, coupled with disposabilityfor pressure sensing pod 80 and the connected venous set 82.

Connector 78 may be an appropriate threaded, locking connector or thelike, preferably one that meets the DIN specifications or any othermeans for a secure connection, including an adhesively bondedconnection, to dialyzer 76 via its conventional connector 77.

Pressure sensing pod 80 connects with blood flow tubing 84 which, inturn, connects with an air trap chamber 86 which may be conventional,for example of a design similar to that disclosed in U.S. Pat. No.6,517,508, the disclosures of which are incorporated by reference, inwhich bubbles are separated by centrifugal flow without suction of thebubbles downwardly by the formation of a vortex. Preferably, air trapchamber 86 may be operated with no upper liquid level or airspace for acompletely airless extracorporeal system, but for bubbles collected.Tubing 88 connects to the bottom of air trap chamber 86 at one end, andconnects to a conventional patient fistula connector 90. Connector port87 is also provided.

Turning to FIG. 8, an exploded view of pressure sensing pod 80 is shown,the structure of pressure sensing pod 68 being also similar to it,except for the elements to which it is connected.

Pressure sensing pod 80 defines a lower compartment portion 22 a,generally similar to the embodiment shown in FIG. 2, including thebottom flow groove 50 a similar to groove 50. Diaphragm 26 a isgenerally of similar design to diaphragm 26, having a bulge 28 a ofslightly different design. Pressure sensing pod 80 is then closed withupper compartment portion 24 a, the peripheries of the portions beingsealed together in a conventional manner.

Port 112 may be used for testing in manufacturing, and may be sealedwith an amount of sealant 114.

Pressure sensing pod 80 carries sealed port 116, which may be generallyof the design of a female luer lock connector, having lugs or screwthreads 118 in conventional manner, or other sealing and/or lockingmeans. Port 116 is sealed by partition 120, so that the volume 92, whichis spaced by diaphragm 28 a from flow ports 30 a, 32 a, is hermeticallysealed when the periphery 94 of pressure sensing pod 80 is sealed.Partition 120 has a peripheral connection with lumen wall 96 of sealedport 116.

The pressure sensing diaphragm in pod 80 defines a dome 28 a which has amaximum depth 29 of about 6-7 mm. (such as 6.3 mm), and a width of thechamber defined by the dome of about 23-25 mm., specifically 24 mm.

As shown particularly in FIG. 9, partition 120 has a 360° peripheralconnection with lumen wall 96, with a major portion 98 of the peripheralconnection being relatively thin, typically a film of sealing materialabout 0.2 to 0.4 mm thick. This thin, frangible peripheral band 98comprises the major portion of the circumference of partition 120, forexample extending from about 270°-330° of the circumference,specifically about 300°.

At the periphery of the remaining portion of the circumference ofpartition 120, a minor portion 100 of the peripheral connection may bethicker, on the order of 1 mm thick, so that it is not frangible but,rather, serves as a hinge to permit partition 120 to pivot as it isbroken open by the pressure of an advancing tubular member, such as amale luer lock connector, advancing through lumen wall 96 of connector116.

Additionally, as shown in FIGS. 8 and 9, a first section 102 ofpartition 120 is positioned adjacent to at least some of the major,thin, peripheral portion 98. This first section 102 is thicker than thecorresponding, opposite section 104 of partition 120 adjacent to theperiphery of minor portion 100. Thus, when a tubular connector 106, asshown in FIG. 11, is advanced into the lumen of connector 116, in thenormal circumstance when tubular male luer lock connector 106 has aflush, tubular end, it engages first, thickened portion 102 of partition120, which is positioned adjacent to major, peripheral portion 98, tofocus rupturing force to at least some of major peripheral portion 98.Thus, inward pressure of tubular connector 106 causes rupturing forcethat is focused onto at least a portion of the thin, major, peripheralportion 98, causing major portion 98 to rip open. Minor peripheralportion 100, however, is thick enough, typically on the order of 1 mm,to not rip, but rather to bend as a hinge, to open connector 116. It isaccordingly desirable for connector 116 and particularly partition 120to be made of a material such as polyethylene, which is capable offorming a reliable, strong hinge upon bending at the hinge thicknessused.

As shown in FIG. 8, pressure sensing pod 80 is attached to a blood flowconnector 78, and thus may be directly, releasably or permanentlyconnected with an extracorporeal blood processing device such asdialyzer 76 (FIG. 10). Connector 78 may be a connector that complieswith DIN standards in a conventional manner.

As shown in FIG. 11, male luer connector 106 may be carried on the endof pressure tubing 42 a in a manner similar to tubing 42 of FIG. 1,except that pressure tubing 42 a is not shown permanently bonded to pod80. Thus, pod 80 may be reversibly or permanently attached to aconnector 41 (FIG. 1) which communicates with an electronic pressuremonitor 43 of the machine. In this present embodiment of FIGS. 10 and11, tubing 42 a, end connector 44 a, and male luer connector 106, havinglocking sleeve 108, may be reusable for a large number of connectionswith different pressure sensing pods 80, since connector 116communicates with volume 92 inside of pressure sensing pod 80, whichvolume is sealed from the blood flow path 31 a, by diaphragm 26 a. Thus,sterility does not have to be an attribute of pressure tubing 42 a. Thispermits the long term or even permanent communication of tubing 42 a andelectronic pressure sensing device 43, wherever remotely located on themachine, and its sequential use with a large number of separate bloodflow sets, such as that of FIG. 7.

Saline line 69 of set 60 provides a connection with pressure chamber orpod 68 in a manner similar to the saline line connection 34 of FIG. 2.Pressure sensing pod 68 also carries a connector 116 a similar instructure and function to connector 116.

The particular design of partition 120 and sealed connector 116 andother disclosed designs, may be used in other modes of use for medicalfluid flow sets, for example, as a sealed port for a Y or T connector,or a connector to another kind of pod or chamber for any of varioususes. The connectors disclosed may be connected to a pump tubing segmentconnector 72 to receive a heparin branch line (not shown), and/or theconnectors may be carried on arterial inlet connectors to receive anattachable injection site. In this way, branch tubing components of theblood set can be reduced or eliminated, for cost savings.

Referring to FIGS. 12-17, a diaphragm chamber or pod 80 a is similar tochamber 80 except as otherwise described. Pod 80 a carries a sealed port116 a, similar to port 116, attached to pod 80 a, and generally of thedesign of a female luer lock connector, having lugs or screw threads 118a in conventional manner or other sealing and/or locking means. Port 116a is sealed by partition 120 a, so that the volume 92 a which is spacedby the diaphragm of pod 80 a (similar to diaphragm 28 a in the previousembodiment) is hermetically sealed when the periphery of pod 80 a issealed, as in the previous embodiment. Partition 120 a has a peripheralconnection with the lumen-defining wall 96 a of port 116 a.

As shown particularly in FIG. 12, partition 120 a has 360 degreeperipheral connection with lumen wall 96 a, with a diametrically opposedpair of peripheral, thin walled tear lines 130, being positionedadjacent to lumen wall 96 a and comprising a major portion of thecircumference of partition 120 a. These tear lines are relatively thin,comprising lines partition wall of material typically about 0.2-0.4 mmthick, depending of course upon the particular plastic used. These thin,frangible peripheral tear lines may extend, for example, at least about250 degrees of the total circumference, and typically no more than about340 degrees.

Partition 120 a also defines a similarly thin-walled tear line 132extending substantially as a diameter across partition 120 a, togenerally bisect partition 120 a by separating it into two, generallysimilar halves.

At the periphery of the remaining portions of the circumference ofpartition 120 a, minor portions of the periphery 134, which are theremaining portions of the circumference, may be thicker than portions130 and 132, being generally on the order of 1 mm thick or more, so asnot to be frangible, but, rather, to serve as hinges to respectivelypermit the two halves of partition 120 a on either side of central, thintear line 132 to pivot as partition 120 a is broken open by the pressureof an advancing tubular member such as male connector 136, which may beconnected to pressure connection tubing 138, for similar purpose astubing 42, 42 a, or for any other desired medical purpose.

Connector 136 may define a projecting, frustoconical sealing member 140which mates in the manner of a luer connector with tapered,frustoconical lumen wall 96 a. Projecting member 140 further carries apartition opening member 142 at its forward end, which, in turn, maycomprise a frustoconical member of greater wall angle to the axis ofconnector 136, or it may comprise a pointed member with open lumen flowports positioned beside it, or any member which can press againstpartition 120 a to rupture lines 130, 132, to open partition 120 a.

Thus, instead of a thickened partition broken by a regular male luer orother tube having a flush end, as in the previous embodiment, in thisembodiment, a partition is provided without thick sections (but havingthe thinned tear lines 130, 132) and which uses an extension 142 on amale connector 140 to break partition 120 a. This has advantage when onedoes not want a regular male luer lock connector or the like tomistakenly access the device, since it can be formed so that a maleconnector engages and seals with frustoconical lumen surface 96 a beforethe male luer can reach partition 120 a to press it, to cause possiblepremature opening. Thus, a special set with a special connector 136 maybe required to open sealed port 116 a.

This special male connector 136 is carried on the end of pressure tubing138, which may be similar to pressure tubing 42 a of FIG. 10, exceptthat pressure tubing 138 is not permanently bonded to pod 80 a and uppercompartment portion 92 a, and may be reversibly or permanently attachedto a pressure port similar to port 41, which communicates with anelectronic pressure monitor 43 of a pressure measuring machine.

In the embodiment of FIGS. 12-17, tubing 138 and special male connector136, having locking sleeve 143, may be reusable for a large number ofconnections with different diaphragmatic chambers or pods 80 a, sinceconnector 116 a is sealed from the blood flow path by its diaphragm.Sterility thus does not have to be an attribute of pressure tubing 138(or tubing 42 a), permitting the long term and even permanent connectionof tubing 138 to electronic pressure sensing system 41, 43, whereverremotely located on the machine, such as a dialysis machine. Thus, asignificant economy may be achieved by the sequential use of tubing 138and connector 136 with a large number of separate blood flow sets.

Referring to FIGS. 18 and 19, a pod 150, defining a chamber 152 and aflexible diaphragm 154, defining a dome in a manner similar to those ofprevious embodiments such as diaphragm 26, is disclosed. Pod 150 may beused in a manner described with respect to pods of the previousembodiments, being connected through tubular connectors 156, 158 totubular components of an extracorporeal blood set, or directly connectedat one of the connectors 156, 158 to a dialyzer or the like, aspreviously described. Port 160 is provided, being for a similar purposeas is port 116, 116 a of the previous embodiment, carrying a partition163, which may be of design similar to the partitions of the previousembodiments and for similar purpose.

It can be seen that pod 150 is elongated, and in some embodiments ofthis invention, the length of pod chamber 152 along its longest axis 153may be at least twice its width 162. This provides a greater volume topod 150 compared with a round pod having a diameter similar to the width162 of pod 150. The dome of diaphragm 154 can flip back and forth in amanner described with respect to previous embodiments, and thus, theoverall volume of the air side 164 of the chamber and go fromessentially zero as shown in FIG. 19 to a volume which is at least 2.5cc, preferably 3.0 cc., and specifically more than 3.2 cc., typically,so that an air volume of that amount can form when flexible diaphragm154 is displaced to its maximum position on the right of FIG. 19, tominimize the volume of blood compartment 166 in pod 150, for theadvantages previously discussed.

Thus, as flexible diaphragm 154 flips its dome between its twopositions, there is a volume displacement, displacing at least 2.5 cc.of air and typically greater amounts as specified above. This amount ofdisplacement assures that a broad pressure range in pod 150 can bemonitored despite using a lengthy tube several feet in length whichconnects port 160 with a pressure transducer mounted within a pressuresensing component of, for example, an extracorporeal blood processingmachine, as in previous embodiments. Specifically, it is desirable forthe system to be able to register a range of 500 mmHg of positivepressure to minus 250 mmHg of reduced or negative pressure without thedome of diaphragm 154 coming into contact with a wall of pod 150 so thatit can no longer move its position responsive to pressure change. It canalso be seen that stretching of the elastomer of diaphragm 154 isminimized by the dome configuration as the dome moves back and forth. Infact, in some embodiments, flexible but non elastomeric materials may beused for the dome 154.

Specifically, to achieve the desired volumes in a small pod, the width162 of diaphragm 154 (essentially the same as the chamber width) shouldbe at least twice the depth 168 of the dome of diaphragm 154 and in someembodiments the width 162 should be at least three times the depth 168of dome 164. This helps to provide a blood flow path, having a maximumthickness which is not too deep, causing a risk of blood stagnation andclotting, while at the same time providing an adequate amount of airdisplacement on the air side of diaphragm 154 so that a wide range ofpressures can be measured.

The above has been offered for illustrative purposes only, and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

1. A tubular blood flow set which comprises: first and second pressuresensing pods, each defining a chamber; said first pod being connected inflow-through relation to an arterial blood flow tubing portion of saidset; said first pod being connected in flow-through relation to a venousblood flow tubing portion of said set; for each of said first and secondpods, a length of pressure tubing connectable at one end with saidchamber thereof via a pressure port thereof, for connection at the otherpressure tubing end with a respective pressure measuring equipmentconnector to permit said each of said first and second pods to be spacedfrom said respective pressure measuring equipment; and said each of saidpods having a flexible diaphragm sealingly mounted within said each ofsaid pods between connections of said arterial and venous blood flowtubing and said pressure tubing, said diaphragm being moveable betweenfirst and second positions, the diaphragm in said first position bowingoutwardly to substantially maximize volume in said chamber thatcommunicates with said blood flow tubing, the diaphragm in said secondposition bowing inwardly to substantially minimize but not eliminate theblood volume in said chamber that is inside of said diaphragm, saiddiaphragm in use being in contact on one side thereof with flowingblood; the pressure port being in communication with said chamber on aside of said diaphragm opposite said connections of said blood flowtubing; said diaphragm having a central dome portion that can flipbetween said first position said second position the first poddiaphragm, prior to use, being arranged in the first position; thesecond pod diaphragm, prior to use, being arranged in the secondposition.
 2. The set of claim 1, wherein each length of pressure tubingis permanently connected by said one end with a respective one of saidchambers via a respective one of said pressure ports.
 3. The set ofclaim 1, wherein the dome portion has a continuous curved cross-section.